Maxim MAX1667EAP Datasheet

General Description

The MAX1667 provides the power control necessary to
charge batteries of any chemistry. All charging functions
are controlled through the Intel System Management Bus
(SMBus™) interface. The SMBus 2-wire serial interface
sets the charge voltage and current and provides thermal
status information. The MAX1667 functions as a Level 2
charger, compliant with the Duracell/Intel Smart Battery
Charger Specification.

In addition to the feature set required for a Level 2 charg­er, the MAX1667 generates interrupts to signal the host
when power is applied to the charger or when a battery is
installed or removed. Additional status bits allow the host
to check whether the charger has enough input voltage,
and whether the voltage on or current into the battery is
being regulated. This allows the host to determine when
lithium-ion (Li+) batteries have completed the charge with­out interrogating the battery.

The MAX1667 is available in a 20-pin SSOP with a 2mm
profile height.

________________________Applications

Notebook Computers Charger Base Stations
Personal Digital Assistants Phones

____________________________Features

♦ Charges Any Battery Chemistry: Li+, NiCd,

NiMH, Lead Acid, etc.

♦ SMBus 2-Wire Serial Interface
♦ Compliant with Duracell/Intel Smart Battery

Charger Specification Rev. 1.0

♦ 4A, 3A, or 1A (max) Battery Charge Current
♦ 5-Bit Control of Charge Current
♦ Up to 18.4V Battery Voltage
♦ 11-Bit Control of Voltage
♦ ±1% Voltage Accuracy
♦ Up to +28V Input Voltage
♦ Battery Thermistor Fail-Safe Protection
♦ Greater than 95% Efficiency
♦ Synchronous Rectifier

MAX1667

Chemistry-Independent,

Level 2 Smart Battery Charger

________________________________________________________________

Maxim Integrated Products

1

Typical Operating Circuit

PART

MAX1667EAP -40°C to +85°C

TEMP. RANGE PIN-PACKAGE

20 SSOP

Ordering Information

For free samples & the latest literature: http://www.maxim-ic.com, or phone [phone].
For small orders, phone [phone].

SMBus is a trademark of Intel Corp.

19-1488; Rev 0; 7/99

MAX1667

DCIN

REF BST

DHI

LX

DLO

PGND

INT

CS

BATT

SCL
SDA

THM

IOUT

VL

CHARGE SOURCE

AGND

SEL

DACV

CCV

CCI

V

DD

HOST

CONTROLLER

SMART

BATTERY

SCL

SDA

INT
GND

BATT+

R

SENSE

SCL
SDA
TEMP
BATT-

Pin Configuration appears at end of data sheet.

MAX1667

Chemistry-Independent,
Level 2 Smart Battery Charger

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(V

DCIN

= 18V, internal reference, 1µF capacitor at REF, 1µF capacitor at VL, TA= 0°C to +85°C, unless otherwise noted. Typical values

are at T

A

= +25°C, unless otherwise noted.)

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.

DCIN to AGND .......................................................-0.3V to +30V

BST to AGND..........................................................-0.3V to +36V

BST, DHI to LX..........................................................-0.3V to +6V

LX, IOUT to AGND..................................................-0.3V to +30V

THM, CCI, CCV, DACV, REF,

DLO to AGND .............................................-0.3V to (VL + 0.3V)

VL, SEL, INT, SDA, SCL to AGND............................-0.3V to +6V

BATT, CS+ to AGND ..............................................-0.3V to +20V

PGND to AGND.....................................................-0.3V to +0.3V

SDA, INT Current ................................................................50mA

VL Current...........................................................................50mA

Continuous Power Dissipation (T

A

= +70°C)

SSOP (derate 8mW/°C above +70°C) ..........................640mW

Operating Temperature Range ...........................-40°C to +85°C

Storage Temperature Range .............................-60°C to +150°C

Lead Temperature (soldering, 10sec) .............................+300°C

%

-0.8 0.8

ChargingVoltage()
= 0x3130 (12,592mV)
and
0x41A0 (16,800mV)

Voltage Accuracy

mV5ChargingCurrent() = 0x0080 (128mA)

CS to BATT Single-Count
Current-Sense Voltage

V019BATT, CS Input Voltage Range

µA

350 500VL > 5.15V, V

BATT

= 12V

BATT Input Current (Note 1)

15VL < 3.2V, V

BATT

= 12V

Ω58High or lowDLO On-Resistance

Ω47High or lowDHI On-Resistance

mA467.5V < V

DCIN

< 28V, logic inputs = VLDCIN Quiescent Current

V7.5 28DCIN Input Voltage Range

%96.5 97.7In dropoutDHI Maximum Duty Cycle

kHz200 250 300Not in dropoutOscillator Frequency

V5.15 5.4 5.657.5V < V

DCIN

< 28V, no loadVL Output Voltage

mV100I

LOAD

= 0 to 10mAVL Load Regulation

V3.20 4 5.15VL AC_PRESENT Trip Point

4.055 4.096 4.137

UNITSMIN TYP MAXCONDITIONSPARAMETER

µA

170 400VL > 5.15V, VCS= 12V

CS Input Current (Note 1)

15VL < 3.2V, VCS= 12V

mV145 160 175

SEL = VL (4A),
ChargingCurrent() = 0x0F80 (3968mA)

CS to BATT Full-Scale
Current-Sense Voltage

V0 < I

SOURCE

< 500µAREF Output Voltage

TA= +25°C

TA= T

MIN

to T

MAX

-1.0 1.0

TA= +25°C

TA= T

MIN

to T

MAX

-3.0 3.0

-1.0 1.0

ChargingVoltage()
= 0x1060 (4192mV)
and
0x20D0 (8400mV)

SWITCHING REGULATOR

SUPPLY AND REFERENCE

MAX1667

Chemistry-Independent,

Level 2 Smart Battery Charger

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(V

DCIN

= 18V, internal reference, 1µF capacitor at REF, 1µF capacitor at VL, TA= 0°C to +85°C, unless otherwise noted. Typical values

are at T

A

= +25°C, unless otherwise noted.)

Note 1: When DCIN is less than 4V, VL is less than 3.2V, causing the battery current to be typically 2µA (CS plus BATT input

current).

Bits11Guaranteed monotonicVDAC Voltage-Setting DAC Resolution

Bits5Guaranteed monotonicCDAC Current-Setting DAC Resolution

mA5

mA579

% of

V

REF

3 4.5 6THM falling

THM THERMISTOR_UR
Underrange Trip Point

% of

V

REF

22 23.5 25THM falling

THM THERMISTOR_HOT
Trip Point

% of

V

REF

74 75.5 77THM falling

THM THERMISTOR_COLD
Trip Point

mA/V0.2GMI Amplifier Transconductance

mA/V1.4GMV Amplifier Transconductance

% of

V

REF

89 91 93THM falling

THM THERMISTOR_OR
Overrange Trip Point

% of

V

DCIN

93 95 97BATT risingBATT POWER_FAIL Threshold

µA±80

GMV Amplifier Maximum
Output Current

µA±200

GMI Amplifier Maximum
Output Current

mV25 80 2001.1V < V

CCI

< 3.5V

CCV Clamp Voltage with
Respect to CCI

UNITSMIN TYP MAXCONDITIONSPARAMETER

mA6V

SDA

= 0.6VSDA Output Low Sink Current

µA-1 1SDA, SCL Input Bias Current

V2.2SDA, SCL Input Voltage High

V0.8SDA, SCL Input Voltage Low

mV25 80 2001.1V < V

CCV

< 3.5V

CCI Clamp Voltage with
Respect to CCV

ChargingCurrent() = 0x0000 10 µA

ChargingCurrent() = 0x0001
to 0x007F (127mA)

V

IOUT

= 17V, ChargingCurrent() = 0x0001

to 0x007F (127mA)
V

DCIN

= 0, V

IOUT

= 20V µA10IOUT Leakage Current

V

IOUT

= 0

IOUT Output Current

% of

V

DCIN

0.5

THM THERMISTOR_OR, _COLD,
_HOT, _UR Trip Point Hysteresis

% of

V

DCIN

1

BATT POWER_FAIL Threshold
Hysteresis

ERROR AMPLIFIERS

TRIP POINTS AND LINEAR CURRENT SOURCES

CURRENT- AND VOLTAGE-SETTING DACs

LOGIC LEVELS

MAX1667

Chemistry-Independent,
Level 2 Smart Battery Charger

4 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS

(V

DCIN

= 18V, internal reference, 1µF capacitor at REF, 1µF capacitor at VL, TA= -40°C to +85°C, unless otherwise noted. Typical values

are at T

A

= +25°C. Limits over this temperature range are guaranteed by design.)

µACS Input Current (Note 1) 5VL < 3.2V, VCS= 12V

mV145 160 175

V

SEL

= VL,

ChargingCurrent() = 0x0F80 (128mA)

CS to BATT Full-Scale
Current-Sense Voltage

%

-1.0 1.0

ChargingVoltage() = 0x3130 (12,592mV),
ChargingVoltage() = 0x41A0 (16,800mV)

Voltage Accuracy

µABATT Input Current (Note 1) 5VL < 3.2V, V

BATT

= 12V

Ω58High or lowDLO On-Resistance

Ω47High or lowDHI On-Resistance

mA467.5V < V

DCIN

< 28V, logic inputs = VLDCIN Quiescent Current

%96.5In dropoutDHI Maximum Duty Cycle

kHz200 250 310Not in dropoutOscillator Frequency

V5.15 5.4 5.657.5V < V

DCIN

< 28V, no loadVL Output Voltage

V4.055 4.1370 < I

SOURCE

< 500µAREF Output Voltage

UNITSMIN TYP MAXCONDITIONSPARAMETER

% of

V

REF

88.5 93.5THM falling

THM THERMISTOR_OR
Overrange Trip Point

% of

V

REF

73.5 77.5THM falling

THM THERMISTOR_COLD
Trip Point

V0.5SDA, SCL Input Voltage Low
V2.2SDA, SCL Input Voltage High

µA-1 1SDA, SCL Input Bias Current

% of

V

REF

21.5 25.5THM falling

THM THERMISTOR_HOT
Trip Point

% of

V

REF

2.5 6.5THM falling

THM THERMISTOR_UR
Underrange Trip Point

mA6V

SDA

= 0.6VSDA Output Low Sink Current

%1

THM THERMISTOR_OR, _COLD,
_HOT, _UR Trip Point Hysteresis

-3.0 3.0

ChargingVoltage() = 0x1060 (4192mV),
ChargingVoltage() = 0x20D0 (8400mV)

SUPPLY AND REFERENCE

SWITCHING REGULATOR

TRIP POINTS AND LINEAR CURRENT SOURCES

LOGIC LEVELS

MAX1667

Chemistry-Independent,

Level 2 Smart Battery Charger

_______________________________________________________________________________________ 5

TIMING CHARACTERISTICS (Figures 1 and 2)

(TA= 0°C to +85°C, unless otherwise noted.)

TIMING CHARACTERISTICS (Figures 1 and 2)

(TA= -40°C to +85°C, unless otherwise noted. Limits over this temperature range are guaranteed by design.)

CONDITIONS

µs1t

DV

SCL Falling Edge to SDA Valid,
Master Clocking in Data

ns0t

HD:DAT

SCL Falling Edge to SDA Transition

µs4.7t

SU:STA

Start-Condition Setup Time

µs4.7t

LOW

µs4t

HIGH

SCL Serial-Clock High Period
SCL Serial-Clock Low Period

µs4t

HD:STA

Start-Condition Hold Time

ns250t

SU:DAT

SDA Valid to SCL Rising-Edge
Setup Time, Slave Clocking in Data

UNITSMIN TYP MAXSYMBOLPARAMETER

CONDITIONS

µs4.7t

SU:STA

Start-Condition Setup Time

µs4.7t

LOW

UNITSMIN TYP MAXSYMBOLPARAMETER

SCL Serial-Clock Low Period

µs4t

HD:STA

Start-Condition Hold Time

µs4t

HIGH

SCL Serial-Clock High Period

ns250t

SU:DAT

SDA Valid to SCL Rising-Edge
Setup Time, Slave Clocking in Data

ns0t

HD:DAT

SCL Falling Edge to SDA Transition

µs1t

DV

SCL Falling Edge to SDA Valid,
Master Clocking in Data

MAX1667

Chemistry-Independent,
Level 2 Smart Battery Charger

6 _______________________________________________________________________________________

Figure 2. SMBus Serial-Interface Timing—Acknowledge

t

DV

SLAVE PULLING
SDA LOW

t

DV

MOST SIGNIFICANT BIT

OF DATA CLOCKED

INTO MASTER

ACKNOWLEDGE

BIT CLOCKED
INTO MASTER

RW BIT

CLOCKED

INTO SLAVE

SCL

SDA

START

CONDITION

MOST SIGNIFICANT

ADDRESS BIT (A6)

CLOCKED INTO SLAVE

A5 CLOCKED

INTO SLAVE

A4 CLOCKED

INTO SLAVE

A3 CLOCKED

INTO SLAVE

t

HIGH

t

LOW

t

HD:STA

t

SU:STA

t

SU:DAT

t

HD:DAT

SCL

SDA

t

SU:DAT

t

HD:DAT

Figure 1. SMBus Serial-Interface Timing—Address

MAX1667

Chemistry-Independent,

Level 2 Smart Battery Charger

_______________________________________________________________________________________

7

__________________________________________Typical Operating Characteristics

(Circuit of Figure 7, TA = +25°C, unless otherwise noted.)

(VOLTAGE REGULATION WITH CURRENT LIMIT)

10V

5V/div

V

DCIN

ChargingVoltage() = 12,000mV
ChargingCurrent() = 1500mA

CCI

CCV

= 18V

LOAD TRANSIENT

CCV

CCI

CCV

CCI

V

BATT

I

LOAD

AVERAGED MEASUREMENT

500µs/div

CCI

CCV

MAX1667TOC01

200mV/div

1.4V

1A
1A/div

(WITH CHANGE IN REGULATION LOOP)

LOAD TRANSIENT

CCV

CCI

I

LOAD

10V

5V/div

V

= 18V

DCIN

ChargingVoltage() = 12,000mV
ChargingCurrent() = 1500mA

CCI

CCV

V

BATT

AVERAGED MEASUREMENT

1ms/div

MAX1667TOC02

CCV

CCI

50mV/div

2V

1A
500mA/div

VL LINE REGULATION

5.450
NO LOAD

5.425

5.400

VL (V)

5.375

5.350

010155 202530

V

(V)

DCIN

VL vs. TEMPERATURE

5.45

5.44

5.43

5.42

5.41

5.40

VL (V)

5.39

5.38

5.37

5.36

5.35

-40 -20 0 20 40 60 80 100
TEMPERATURE (°C)

V

DCIN

= 20V

MAX1667 TOC03

MAX1667 TOC05

VL LOAD REGULATION

5.50

5.45

5.40

5.35

VL (V)

5.30

5.25

5.20
0105 152025

LOAD CURRENT (mA)

V

LOAD REGULATION

REF

0 0.80.60.2 0.4 1.0 1.2 1.4 1.6 1.8 2.0

LOAD CURRENT (mA)

(V)

V

4.11

4.10

4.09

REF

4.08

4.07

4.06

V

= 20V

DCIN

MAX1667 TOC04

MAX1667 TOC06

MAX1667

Chemistry-Independent,
Level 2 Smart Battery Charger

8 _______________________________________________________________________________________

Typical Operating Characteristics (continued)

(Circuit of Figure 7, TA = +25°C, unless otherwise noted.)

100

0.01

10

1.0

0.1

0.001

0 400 800 1200 1600 2000

OUTPUT V-I CHARACTERISTIC

(SWITCHING REGULATOR)

MAX1667 TOC10

LOAD CURRENT (mA)

DROP IN BATT OUTPUT VOLTAGE (%)

V

DCIN

= 20V
ChargingVoltage() = 17,408mV
ChargingCurrent() = 1920mA
V

REF

= 4.096V

0

5

1

3

4

8

02468101214161820

OUTPUT V-I CHARACTERISTIC

(LINEAR SOURCE)

MAX1667 TOC11

V

IOUT

(V)

I

IOUT

(mA)

2

6

7

V

DCIN

= 20V
ChargingVoltage() = 17,408mV
ChargingCurrent() = 1 to 127mA

4.080

4.100

4.085

4.090

4.095

4.110

-40 4020-20 0 60 80 100

V

REF

vs. TEMPERATURE

MAX1667 TOC07

TEMPERATURE (°C)

V

REF

(V)

4.105

V

DCIN

= 20V

50

70

55

60

65

100

0 20001000 3000 4000

EFFICIENCY vs. LOAD CURRENT

(VOLTAGE REGULATION)

MAX1667 TOC08

LOAD CURRENT (mA)

EFFICIENCY (%)

75

80

85

90

95

A: V

DCIN

= 20V, V

BATT

= 17V

B: V

DCIN

= 16V, V

BATT

= 12.75V

C: V

DCIN

= 20V, V

BATT

= 12.75V

D: V

DCIN

= 16V, V

BATT

= 8.5V

E: V

DCIN

= 20V, V

BATT

= 8.5V

A

B

C

E

D

50

70

55

60

65

100

0862 4 10 12 18

EFFICIENCY vs. BATT VOLTAGE

(CURRENT REGULATION)

MAX1667 TOC09

BATT VOLTAGE (V)

EFFICIENCY (%)

75

80

85

90

95

14 16

A: V

DCIN

= 16V, I

LOAD

= 2A

B: V

DCIN

= 20V, I

LOAD

= 2A

C: V

DCIN

= 20V, I

LOAD

= 600mA

A

B

C

BATT VOLTAGE ERROR (%)

BATT VOLTAGE ERROR

vs. ChargingVoltage() CODE

1.0

0.8

V

= 20V

DCIN

MEASURED AT AVAILABLE

0.6
ChargingVoltage() CODES

0.4

0.2

0

-0.2

-0.4

-0.6

-0.8

-1.0
0 4k6k8k2k 10k 12k 14k 18k16k 20k

ChargingVoltage() CODE

I

LOAD

I

LOAD

= 600mA

= 3mA

MAX1667 TOC12

LOAD CURRENT ERROR

15

10

5

BATT CURRENT ERROR (%)

0

-5

V

=20V

DCIN

V

= 12.75V

BATT

MEASURED AT AVAILABLE
ChargingCurrent() CODES

0 1000 2000 3000500 1500 2500 3500 4000

CODE

MAX1667 TOC13

MAX1667

Chemistry-Independent,

Level 2 Smart Battery Charger

_______________________________________________________________________________________ 9

Pin Description

Linear Current-Source Output1 IOUT
Input Voltage for Powering Charger2 DCIN

Voltage-Regulation-Loop Compensation Point4 CCV

IC Power Supply. 5.4V linear-regulator output from DCIN.3 VL

Current-Range Selector. Connecting SEL to VL sets a 4A full-scale current. Leaving SEL
open sets a 3A full-scale current. Connecting SEL to AGND sets a 1A full-scale current.

6 SEL

Battery Voltage Input and Current-Sense Negative Input8 BATT

Current-Sense Positive Input7 CS

Current-Regulation-Loop Compensation Point5 CCI

+4.096V Reference Voltage Output or External Reference Input9 REF

Open-Drain Interrupt Output11

INT

Analog Ground10 AGND

Thermistor Sense Voltage Input12 THM

Serial Data (need external pull-up resistor)14 SDA

Power Ground16 PGND

Voltage DAC Output Filtering Point15 DACV

Serial Clock (need external pull-up resistor)13 SCL

High-Side Power MOSFET Driver Output18 DHI

Power Connection for the High-Side Power MOSFET Driver20 BST

Power Connection for the High-Side Power MOSFET Driver19 LX

Low-Side Power MOSFET Driver Output17 DLO

FUNCTIONPIN NAME

MAX1667

Chemistry-Independent,
Level 2 Smart Battery Charger

Smart Battery Charging System

A smart battery charging system, at a minimum, con­sists of a smart battery and smart battery charger com­patible with the Smart Battery System specifications
using Intel’s system management bus (SMBus).

Smart Battery System Block Diagrams

A system may use one or more smart batteries. The
block diagram of a smart battery charging system
shown in Figure 3 depicts a single battery system. This
is typically found in notebook computers, video cam­eras, cellular phones, and other portable electronic
equipment.

Another possibility is a system that uses two or more
smart batteries. A block diagram for a system featuring
multiple batteries is shown in Figure 4. The smart bat­tery selector is used to connect batteries to either the
smart battery charger or the system, or to disconnect
them, as appropriate. For a standard smart battery, the
following connections must be made: power (the bat-

tery’s positive and negative terminals), SMBus (clock
and data), and safety signal (resistance, typically tem­perature dependent). Additionally, the system host
must be able to query any battery in the system so it
can display the state of all batteries present in the sys­tem.

Figure 4 shows a two-battery system where Battery 2 is
being charged while Battery 1 is powering the system.
This configuration may be used to “condition” Battery
1, allowing it to be fully discharged prior to recharge.

Smart Battery Charger Types

Two types of smart battery chargers are defined: Level
2 and Level 3. All smart battery chargers communicate
with the smart battery using the SMBus; the two types
differ in their SMBus communication mode and in
whether they modify the charging algorithm of the
smart battery as shown in Table 1. Level 3 smart bat­tery chargers are supersets of Level 2 chargers and as
such support all Level 2 charger commands.

SYSTEM
POWER

CONTROL

AC-DC

CONVERTER

(UNREGULATED)

AC

SYSTEM
POWER
SUPPLY

DC (UNREGULATED) / V

BATTERY

SAFETY
SIGNAL

V

BATTERY

DC (UNREGULATED)

V

CC

+12V, -12V

SYSTEM HOST
(SMBus HOST)

SMART BATTERY

CRITICAL EVENTS

CRITICAL EVENTS

CHARGING VOLTAGE/CURRENT

REQUESTS

BATTERY DATA/STATUS REQUESTS

SMART BATTERY

CHARGER

SMBus

MAX1667

Figure 3. Typical Single Smart Battery System

10 ______________________________________________________________________________________

MAX1667

Chemistry-Independent,

Level 2 Smart Battery Charger

______________________________________________________________________________________ 11

Level 2 Smart Battery Charger

The Level 2 or “smart-battery-controlled” smart battery
charger interprets the smart battery’s critical warning

messages, and operates as an SMBus slave device
that responds to ChargingVoltage() and Charging­Current() messages sent to it by a smart battery. The
charger is obliged to adjust its output characteristics in
direct response to the messages it receives from the
battery. In Level 2 charging, the smart battery is com­pletely responsible for initiating communication and for
providing the charging algorithm to the charger. The
smart battery is in the best position to tell the smart bat­tery charger how it needs to be charged. The charging
algorithm in the battery may request a static charge
condition or may choose to periodically adjust the
smart battery charger’s output to meet its present
needs. A Level 2 smart battery charger is truly chem­istry independent, and since it is defined as an SMBus
slave device only, it is relatively inexpensive and easy
to implement.

Table 1. Charger Type by SMBus Mode
and Charge Algorithm Source

Level 3Level 3Slave/Master

Level 3Level 2

Modified from BatteryBattery

Slave Only

SMBus MODE

CHARGE ALGORITHM SOURCE

Note: Level 1 smart battery chargers are defined in the ver-

sion 0.95a specification. While they can correctly interpret
smart battery end-of-charge messages minimizing over­charge, they do not provide truly chemistry-independent
charging. They are no longer defined by the Smart Battery
Charger specification and are explicitly not compliant with this
and subsequent Smart Battery Charger specifications.

AC-DC

CONVERTER

(UNREGULATED)

AC

DC (UNREGULATED) / V

BATTERY

NOTE: SB 1 POWERING SYSTEM
SB 2 CHARGING

V

CC

+12V, -12V

SYSTEM HOST
(SMBus HOST)

SMART BATTERY

SELECTOR

SMBus

SMBus

SMBus

SAFETY SIGNAL

V

CHARGE

V

BATT

SAFETY

SIGNAL

V

BATT

SAFETY

SIGNAL

SMART BATTERY 1

SMART BATTERY 2

CRITICAL EVENTS

BATTERY DATA/STATUS REQUESTS

SMART BATTERY

CHARGER

SMBus

MAX1667

SYSTEM
POWER
SUPPLY

Figure 4. Typical Multiple Smart Battery System

MAX1667

Chemistry-Independent,
Level 2 Smart Battery Charger

12 ______________________________________________________________________________________

_______________Detailed Description

Output Characteristics

The MAX1667 contains both a voltage-regulation loop
and a current-regulation loop. Both loops operate inde­pendently of each other. The voltage-regulation loop
monitors BATT to ensure that its voltage never exceeds
the voltage set point (V0). The current-regulation loop
monitors current delivered to BATT to ensure that it
never exceeds the current-limit set point (I0). The cur­rent-regulation loop is in control as long as BATT volt­age is below V0. When BATT voltage reaches V0, the
current loop no longer regulates, and the voltage-regu­lation loop takes over. Figure 5 shows the V-I character­istic at the BATT pin.

Setting V0 and I0

Set the MAX1667’s voltage and current-limit set points
via the Intel SMBus 2-wire serial interface. The
MAX1667’s logic interprets the serial-data stream from
the SMBus interface to set internal digital-to-analog con­verters (DACs) appropriately. The power-on-reset value
for V0 and I0 is 18.4V and 7mA, respectively. See

Digital

Section

for more information.

_____________________Analog Section

The MAX1667 analog section consists of a current­mode pulse-width-modulated (PWM) controller and two
transconductance error amplifiers—one for regulating
current and the other for regulating voltage. The device
uses DACs to set the current and voltage level, which
are controlled via the SMBus interface. Since separate
amplifiers are used for voltage and current control, both

control loops can be compensated separately for opti­mum stability and response in each state.

Whether the MAX1667 is controlling the voltage or cur­rent at any time depends on the battery’s state. If the
battery has been discharged, the MAX1667’s output
reaches the current-regulation limit before the voltage
limit, causing the system to regulate current. As the bat­tery charges, the voltage rises until the voltage limit is
reached, and the charger switches to regulating voltage.
The transition from current to voltage regulation is done
by the charger and need not be controlled by the host.
Figure 6 shows the MAX1667 block diagram.

Voltage Control

The internal GMV amplifier controls the MAX1667’s out­put voltage. The voltage at the amplifier’s noninverting
input is set by an 11-bit DAC, which is controlled by a
ChargingVoltage() command on the SMBus (see

Digital

Section

for more information). The battery voltage is fed
to the GMV amplifier through a 5:1 resistive voltage
divider. The set voltage ranges between 0 and 18.416V
with 16mV resolution. This allows up to four Li+ cells in
series to be charged.

The GMV amplifier’s output is connected to the CCV
pin, which compensates the voltage-regulation loop.
Typically, a series-resistor/capacitor combination can
be used to form a pole-zero doublet. The pole intro­duced rolls off the gain starting at low frequencies. The
zero of the doublet provides sufficient AC gain at mid­frequencies. The output capacitor then rolls off the mid­frequency gain to below 1 to guarantee stability before
encountering the zero introduced by the output capaci­tor’s equivalent series resistance (ESR). The GMV
amplifier’s output is internally clamped to between one­fourth and three-fourths of the voltage at REF.

Current Control

An internal 7mA linear current source is used in con­junction with the PWM regulator to set the battery
charge current. When the current is set to 0, the voltage
regulator is on but no current is available. A current set­ting between 1mA and 127mA turns on the linear cur­rent source, providing a maximum of 7mA for trickle
charging. For current settings above 127mA, the linear
current source is disabled and the charging current is
provided by the switching regulator set by the 5-bit cur­rent-control DAC.

The GMI amplifier’s noninverting input is driven by a 4:1
resistive voltage divider, which is driven by the 5-bit
DAC. With the internal 4.096V reference, this input is
approximately 1.0V at full scale, and the resolution is
31mV. The current-sense amplifier drives the inverting
input to the GMI amplifier. It measures the voltage

Figure 5. Output V-I Characteristic

BATT

VOLTAGE

V0

V0 = VOLTAGE SET POINT
I0 = CURRENT-LIMIT SET POINT

AVERAGE CURRENT
THROUGH THE RESISTOR

I0

BETWEEN CS AND BATT

MAX1667

Chemistry-Independent,

Level 2 Smart Battery Charger

______________________________________________________________________________________ 13

Figure 6. Functional Diagram

REF

THM

AGND

CS

BATT

FROM LOGIC

BLOCK

FROM LOGIC BLOCK

BATT

FROM LOGIC BLOCK

10k 10k

100k

CURRENT-SENSE

LEVEL SHIFT AND

GAIN OF 5.5

5

5-BIT DAC

AGND

4R

R

AGND

30k 3k

REF

11

10k

3R

R

TO LOGIC BLOCK

TO LOGIC BLOCK

REF

11-BIT DAC

10k

500Ω

VOLTAGE_INREG

CURRENT_INREG

THERMISTOR_OR

THERMISTOR_COLD

THERMISTOR_HOT

THERMISTOR_UR

CCI

GMI

CLAMP

GMV

CCV

DACV

LOGIC

BLOCK

CCV_LOW

3/8 REF = ZERO CURRENT

NOTE: APPROX. REF/4 + V
TO 3/4 REF + V

MIN

THRESH

NOTE:
REF/4 TO 3/4 REF

CLAMP
TO REF

(MAX)

AGND

THERM_SHUT

SEL

SCL

SDA

INT

AC_PRESENT

THRESH

FROM LOGIC

BLOCK

7mA

THERMAL

SHUTDOWN

DCIN

5.4V LINEAR
REGULATOR

R

AGND

LEVEL
SHIFT

SUMMING

COMPARATOR

BLOCK

DCIN

MAX1667

IOUT

VL

INTERNAL

4.096V

REFERENCE

AGND

CCV

3R

REF

BST

DRIVER

LX

VL

DRIVER

PGND

REF

DHI

DLO

AGND

TO LOGIC BLOCK

POWER_FAIL

DCIN/4.5

MAX1667

Chemistry-Independent,
Level 2 Smart Battery Charger

14 ______________________________________________________________________________________

across the current-sense resistor (R

SEN

) (which is
between the CS and BATT pins), amplifies it by approx­imately 5.45, and level shifts it to ground. The full-scale
current is approximately 0.16V/R

SEN

, and the resolution

is 5mV/R

SEN

.

The current-regulation loop is compensated by adding a
capacitor to the CCI pin. This capacitor sets the current­feedback loop’s dominant pole. The GMI amplifier’s out­put is clamped to between approximately one-fourth
and three-fourths of the REF voltage. While the current is
in regulation, the CCV voltage is clamped to within
80mV of the CCI voltage. This prevents the battery volt­age from overshooting when the DAC voltage setting is
updated. The converse is true when the voltage is in
regulation and the current is not at the current DAC set­ting. Since the linear range of CCI or CCV is about 1.5V
to 3.5V (about 2V), the 80mV clamp results in a relatively
negligible overshoot when the loop switches from volt­age to current regulation or vice versa.

PWM Controller

The battery voltage or current is controlled by the cur­rent-mode, PWM, DC-DC converter controller. This con­troller drives two external N-channel MOSFETs, which
switch the voltage from the input source. This switched
voltage feeds an inductor, which filters the switched rec­tangular wave. The controller sets the pulse width of the
switched voltage so that it supplies the desired voltage
or current to the battery.

The heart of the PWM controller is the multi-input com­parator. This comparator sums three input signals to
determine the pulse width of the switched signal, set­ting the battery voltage or current. The three signals are
the current-sense amplifier’s output, the GMV or GMI
error amplifier’s output, and a slope-compensation sig­nal, which ensures that the controller’s internal current­control loop is stable.

The PWM comparator compares the current-sense
amplifier’s output to the lower output voltage of either
the GMV or the GMI amplifier (the error voltage). This
current-mode feedback corrects the duty ratio of the
switched voltage, regulating the peak battery current
and keeping it proportional to the error voltage. Since
the average battery current is nearly the same as the
peak current, the controller acts as a transconductance
amplifier, reducing the effect of the inductor on the out­put filter LC formed by the output inductor and the bat­tery’s parasitic capacitance. This makes stabilizing the
circuit easy, since the output filter changes from a com­plex second-order RLC to a first-order RC. To preserve
the inner current-control loop’s stability, slope compen­sation is also fed into the comparator. This damps out

perturbations in the pulse width at duty ratios greater
than 50%.

At heavy loads, the PWM controller switches at a fixed
frequency and modulates the duty cycle to control the
battery voltage or current. At light loads, the DC current
through the inductor is not sufficient to prevent the cur­rent from going negative through the synchronous recti­fier (Figure 7, M2). The controller monitors the current
through the sense resistor R

SEN

; when it drops to zero,
the synchronous rectifier turns off to prevent negative
current flow.

MOSFET Drivers

The MAX1667 drives external N-channel MOSFETs to
regulate battery voltage or current. Since the high-side
N-channel MOSFET’s gate must be driven to a voltage
higher than the input source voltage, a charge pump is
used to generate such a voltage. The capacitor C7
(Figure 7) charges to approximately 5V through D2
when the synchronous rectifier turns on. Since one side
of C7 is connected to the LX pin (the source of M1), the
high-side driver (DHI) can drive the gate up to the volt­age at BST (which is greater than the input voltage)
when the high-side MOSFET turns on.

The synchronous rectifier may not be completely
replaced by a diode because the BST capacitor
charges while the synchronous rectifier is turned on.
Without the synchronous rectifier, the BST capacitor
may not fully charge, leaving the high-side MOSFET
with insufficient gate drive to turn on. Use a small MOS­FET, such as a 2N7002, to guarantee that the BST
capacitor is allowed to charge. In this case, most of the
current at high currents is carried by the Schottky diode
and not by the synchronous rectifier.

Internal Regulator and Reference

The MAX1667 uses an internal low-dropout linear regula­tor to create a 5.4V power supply (VL), which powers its
internal circuitry. VL can supply up to 20mA, less than
10mA powers the internal circuitry, and the remaining
current can power the external circuitry. The current
used to drive the MOSFETs comes from this supply,
which must be considered when calculating how much
power can be drawn. To estimate the current required to
drive the MOSFETs, multiply the total gate charge of
each MOSFET by the switching frequency (typically
250kHz). To ensure VL stability, bypass the VL pin with a
1µF or greater capacitor.

The MAX1667 has an internal, accurate 4.096V refer­ence voltage. This guarantees a voltage-setting accu­racy of ±1% max. Bypass the reference with a 1µF or
greater capacitor.

MAX1667

Chemistry-Independent,

Level 2 Smart Battery Charger

______________________________________________________________________________________ 15

Figure 7. Typical Application Circuit

AGND

D2

C9

R5

R6

C6

M1

M2

D1

D4*

D3

DC SOURCE

C1

L1

D5

R1

C7

C11

REF

R3

C4

C10

THM

CCI

IOUT

C5

(NOTE 2)

10

1

2

6

3

20

18

19

17

16

7

8

13

14

11

9

12

5

4

15

= HIGH-CURRENT TRACES (8A MAX)

NOTE 1: C6, M2, D1, AND C1 GROUNDS MUST CONNECT TO
THE SAME RECTANGULAR PAD ON THE LAYOUT.
NOTE 2: C5 AND C11 MUST BE PLACED WITHIN 0.5cm OF THE

MAX1667, WITH TRACES NO LONGER THAN 1cm
CONNECTING VL AND PGND.

*OPTIONAL (SEE

NEGATIVE INPUT VOLTAGE PROTECTION

SECTION).

SEE TABLES 2a AND 2b FOR COMPONENT SELECTION AND MANUFACTURERS.

C8

C2

R2

C3

R4

DCIN

MAX1667

SEL

VL

BST

CCV

DACV

LX

DLO

PGND

CS

DHI

(NOTE 1)

SMART BATTERY

STANDARD CONNECTOR

-TD C+

BATT

SCL

SDA

INT

HOST & LOAD

SMBCLOCK

V+

SMBDATA

KINT-

GND

7.5V–28V

MAX1667

Chemistry-Independent,
Level 2 Smart Battery Charger

16 ______________________________________________________________________________________

Table 2a. Component Selection

_____________________Digital Section

SMBus Interface

The MAX1667 uses serial data to control its operation. The
serial interface complies with the SMBus specification (see

System Management Bus Specification

, from the SBS
forum at www.sbs-Forum.org or from Intel Architecture
Labs: 800-253-3696). Charger functionality complies with
the Duracell/Intel Smart Charger Specification for a Level 2
charger.

The MAX1667 uses the SMBus Read-Word and Write­Word protocols to communicate with the battery it is
charging, as well as with any host system that monitors
the battery to charger communications. The MAX1667
acts only as a slave device and never initiates communi­cation on the bus; it receives commands and responds
to queries for status information. Figures 8a and 8b show
the SMBus Write-Word and Read-Word protocols.

Each communication with the MAX1667 begins with the
master issuing a START condition, which is a high-to­low transition on SDA while SCL is high (Figure 1).

DESIGNATION MANUFACTURER

M2

Low-Side MOSFET

C8

R1

Sense Resistor

40mΩ ±1%, 1W

2N7002 equivalent

D2, D3 Central

Sprague 594D686X0025R2T

C1

Output Capacitor

TPSE686M020R0150

68µF, 20V, low ESR

IRF7805

M1

High-Side MOSFET

IR IRF7603 IRF7201

R5, R6 33Ω ±5%, 1/16W

R3 10kΩ ±1%, 1/16W

R2, R4 10kΩ ±5%, 1/16W

4A1A 3A

C4, C5, C9, C10 1µF

C2, C7, C11

C3 47nF

0.1µF

C6

Input Capacitor

Sprague 594D226X0035R2T

TPSE226M035R0200

2 x 22µF, 35V, low ESR

D1, D4, D5

Schottky Diodes

Central CMSH3-40 CMSH5-40

MBRS130LT3 MBRS340T3

1N5819 equivalent 1N5821 equivalent

MBRS340T3

1N5821 equivalent

AVX

AVX

Motorola

Motorola MMBF1170LT1

L1

Inductor

33µH, 1A ISAT 33µH, 3A ISAT, 30V 33µH, 4A ISAT, 30V

Sumida CDH74-330 CDRH127-330 CDRH127-270

Coiltronics UP1B-330 UP3B-330

Coilcraft DS3316P-333

FDS6680Fairchild FDN359A FDS4410

Motorola MTSF3N03HD MMDF3N03HD

IRC LR251201R040F

Dale WSL-2512/0.04W/±1%

22nF

Schottky diode, 50mA IDC, 30V, CMPSH-3

NIEC EC31 NSQ03A04 CMSH5-40

MAX1667

Chemistry-Independent,

Level 2 Smart Battery Charger

______________________________________________________________________________________ 17

When the master has finished communicating with the
slave, the master issues a STOP condition, which is a
low-to-high transition on SDA while SCL is high. The
bus is then free for another transmission. Figures 1 and
2 show timing diagrams for signals on the SMBus inter­face. The address byte, control byte, and data bytes
are transmitted between the START and STOP condi­tions. Data is transmitted in 8-bit words, and after each
byte either the slave or the master issues an acknowl­edgment (Figure 2); therefore, nine clock cycles are
required to transfer each byte. The SDA state is allowed
to change only while SCL is low, except for the START
and STOP conditions.

The MAX1667 7-bit address is preset to 0b0001001.
The eighth bit indicates a Write-Word (W = 0) or a
Read-Word (R = 1) command. This can also be denot­ed by the hexadecimal number 0x12 for a Write-Word
command or a 0x13 for a Read-Word command.

The following commands use the Write-Word protocol
(Figure 8a): ChargerMode(), ChargingVoltage(),
ChargingCurrent(), and AlarmWarning(). The
ChargerStatus command uses the Read-Word protocol
(Figure 8b).

ChargerMode()

The ChargerMode() command uses Write-Word protocol
(Figure 8a). The command code for ChargerMode() is
0x12 (0b00010010). Table 3 describes the functions of
the 16 data bits (D0–D15). Bit 0 refers to the D0 bit in the
Write-Word protocol.

Whenever the BATTERY_PRESENT status bit (bit 14) of
ChargerStatus() is clear, the HOT_STOP bit is set,
regardless of any previous ChargerMode() command.

To charge a battery that has a thermistor impedance
in the HOT range (i.e., THERMISTOR_HOT = 1 and
THERMISTOR_UR = 0), the host must use the
ChargerMode() command to clear HOT_STOP after the
battery is inserted. The HOT_STOP bit returns to its
default power-up condition (‘1’) whenever the battery is
removed.

ChargingVoltage()

The ChargingVoltage() command uses Write-Word proto­col (Figure 8a). The command code for ChargingVoltage()
is 0x15 (0b00010101). The 16-bit binary number formed
by D15–D0 represents the voltage set point (V0) in milli­volts; however, since the MAX1667 has only 16mV of reso­lution in setting V0, the D0, D1, D2, and D3 bits are
ignored.

The maximum voltage delivered by the MAX1667 is

18.416V, corresponding to a ChargingVoltage() value of
0x47F0. This is also the floating voltage set by the
power-on reset (POR). ChargingVoltage() values above
0x47F0 deliver the floating voltage and set the VOLT­AGE_OR status bit. Any time the BATTERY_PRESENT
status bit is clear, the ChargingVoltage() register
returns to its POR state.

Figure 9 shows the mapping between V0 (the voltage­regulation-loop set point) and the ChargingVoltage()
data.

ChargingCurrent()

The ChargingCurrent() command uses Write-Word proto­col (Figure 8a). The command code for ChargingCurrent()
is 0x14 (0b00010100). The 16-bit binary number formed
by D15–D0 represents the current-limit set point (I0) in
milliamps (Table 4). Connecting SEL to AGND selects a

0.896A maximum setting for I0. Leaving SEL open selects
a 2.944A maximum setting for I0. Connecting SEL to VL
selects a 3.968A maximum setting for I0.

Two sources of current in the MAX1667 charge the bat­tery: a linear current source begins from IOUT, and a
switching regulator controls the current flowing through
the current-sense resistor (R1). IOUT provides a trickle­charge current to compensate for battery self-discharge,
while the switching regulator provides large currents for
fast charging.

IOUT sources 7mA, while the switching regulator
sources from 128mA to 3968mA with a 5-bit resolution
(LSB = 5.12mV / RSENSE = 128mA with a 40mΩ sense
resistor). In Table 4, DA4–DA0 denotes the bits in the
current DAC code. Table 5 shows the relationship
between the value programmed with the Charging­Current() command and IOUT source current. The
CCV_LOW comparator checks to see if the output volt-

Table 2b. Component Suppliers

847-639-1469847-639-6400Coilcraft

516-435-1824516-435-1110

803-626-3123803-946-0690AVX

Central Semiconductor

561-241-9339561-241-7876Coiltronics

FAXPHONEMANUFACTURER

512-992-3377512-992-7900IRC

310-322-3332310-322-3331

605-665-1627605-668-4131Dale

IR

805-867-2698805-867-2555NIEC

603-224-1430603-224-1961

408-970-3950408-988-8000Siliconix

Sprague

847-956-0702847-956-0666Sumida
516-864-7630516-543-7100Zetex

MAX1667

Chemistry-Independent,
Level 2 Smart Battery Charger

18 ______________________________________________________________________________________

age is too high by comparing CCV to REF/4. If
CCV_LOW = 1 (when CCV < REF/4), IOUT shuts off.
This prevents the output voltage from exceeding the
voltage set point specified by the ChargingVoltage()
register. VOLTAGE_NOTREG = 1 whenever the internal
clamp pulls down on CCV. (The internal clamp pulls
down on CCV to keep its voltage close to CCI’s volt­age.)

With the switching regulator on, the current through R1
(Figure 7) is regulated by sensing the average voltage
between CS and BATT. Figure 10 shows the relation­ship between the ChargingCurrent() data and the aver­age voltage between CS and BATT.

When the switching regulator is off, DHI is forced to
LX and DLO is forced to ground. This prevents current
from flowing through inductor L1. Table 6 shows the
relationship between the ChargingCurrent() register
value and the switching regulator current DAC code
(DA4–DA0).

To ensure that the actual output current matches the
data value programmed with the ChargingCurrent()
command, R1 should be as close as possible to 40mΩ.
The SEL pin setting affects the full-scale current but not
the step size. ChargingCurrent() values above the full-

scale setting set the CURRENT_OR status bit. Note that
whenever any current DAC bits are set, the linear-cur­rent source is turned off.

The power-on reset value for the ChargingCurrent() reg­ister is 0x0007. Any time the BATTERY_PRESENT status
bit is clear (battery removed), the ChargingCurrent()
register returns to its power-on reset state. This ensures
that upon insertion of a battery, the initial charging cur­rent is 7mA.

AlarmWarning()

The AlarmWarning() command uses Write-Word protocol
(Figure 8a). The command code for AlarmWarning() is
0x16 (0b00010110). The AlarmWarning() command sets
the ALARM_INHIBITED status bit. The MAX1667 responds
to the following alarms: OVER_CHARGED_ALARM (D15),
TERMINATE_CHARGE_ALARM (D14), and OVER_TEMP_
ALARM (D12). Table 7 summarizes the AlarmWarning()
command’s function. The ALARM_INHIBITED status bit
remains set until BATTERY_PRESENT = 0 (battery
removed), a ChargerMode() command is written with the
POR_RESET bit set, or a new ChargingVoltage() or
ChargingCurrent() is written.

—7–9N/A

05

—4N/A

BATTERY_PRESENT_MASK

—

11–15
(MSB)

N/A Not implemented. Write 1 into this bit.

110HOT_STOP

Not implemented. Write 1 into this bit.

0 = Interrupt on either edge of the BATTERY_PRESENT status bit.
1 = Do not interrupt because of a BATTERY_PRESENT bit change.

Not implemented. Write 1 into this bit.

0 = The THERMISTOR_HOT status bit does not turn the charger off.
1 = THERMISTOR_HOT turns the charger off.

0 = No change in any non-ChargerMode() settings.
1 = Change the voltage and current settings to 0xFFFF and 0x0007
respectively; clear the THERMISTOR_HOT and ALARM_INHIBITED bits.

Not implemented. Write 0 into this bit.

0 = Allow normal operation; clear the CHG_INHIBITED status bit.
1 = Turn the charger off; set the CHG_INHIBITED status bit.

Not implemented. Write 0 into this bit.

FUNCTION

—2POR_RESET

—1

0

0

(LSB)

INHIBIT_CHARGE

ENABLE_POLLING

—3RESET_TO_ZERO

POR

VALUE**

BIT

POSITION*

BIT NAME

Table 3. ChargerMode() Bit Functions

16POWER_FAIL_MASK

0 = Interrupt on either edge of the POWER_FAIL status bit.
1 = Do not interrupt because of a POWER_FAIL bit change.

*

Bit position in the D15–D0 data. **Power-on reset value.

N/A = Not applicable

MAX1667

Chemistry-Independent,

Level 2 Smart Battery Charger

______________________________________________________________________________________ 19

ChargerStatus()

The ChargerStatus() command uses Read-Word proto­col (Figure 8b). The command code for ChargerStatus()
is 0x13 (0b00010011). The ChargerStatus() command
returns information about thermistor impedance and the
MAX1667’s internal state. The Read-Word protocol
returns D15–D0. Table 8 describes the meaning of the
individual bits. The latched bits, THERMISTOR_HOT
and ALARM_INHIBITED, are cleared whenever BAT­TERY_PRESENT = 0 or ChargerMode() is written with
POR_RESET = 1.

Interrupts and the

Alert-Response Address

An interrupt is triggered (INT goes low) whenever power
is applied to DCIN, the BATTERY_PRESENT bit changes,
or the POWER_FAIL bit changes. BATTERY_PRESENT
and POWER_FAIL have interrupt masks that can be set

or cleared via the ChargerMode() command. INT stays
low until the interrupt is cleared. There are two methods
for clearing the interrupt: issuing a ChargerStatus() com­mand, and using a modified Receive Byte protocol with a
0x19 (0b0011001) Alert-Response address. The
MAX1667 responds to the Alert-Response address with
its address (0x13) left justified as the most significant bits
of the returned byte.

__________Applications Information

Negative Input Voltage Protection

In most portable equipment, the DC power to charge
batteries enters through a two-conductor cylindrical
power jack. It is easy for the end user to add an
adapter to switch the DC power’s polarity. Polarized
capacitor C6 would be destroyed if a negative voltage
were applied. Diode D4 in Figure 7 prevents this from
happening.

Figure 8. SMBus a) Write-Word and b) Read-Word Protocols

0MSB LSB

1b7 bits

W

SLAVE

ADDRESS

S

1b

ACK S

MSB LSB

1b8 bits

ACK

COMMAND

BYTE

1b

ACK

1MSB LSB

1b7 bits

R

SLAVE

ADDRESS

MSB LSB

1b8 bits

ACK

LOW
DATA
BYTE

P

MSB LSB

1b8 bits

NACK

HIGH

DATA

BYTE

Preset to

0b0001001

D7 D0 D15 D8

ChargerMode() = 0x12
ChargingCurrent() = 0x14
ChargerVoltage() = 0x15
AlarmWarning() = 0x16

Preset to

0b0001001

Preset to

0b0001001

D7 D0 D15 D8

ChargerStatus() =

0x13

1b

ACK S

MSB LSB

1b8 bits

ACK

COMMAND

BYTE

0MSB LSB

1b7 bits

W

SLAVE

ADDRESS

S

MSB LSB

1b7 bits

ACK

LOW

DATA

BYTE

P

MSB LSB

1b8 bits

ACK

HIGH
DATA
BYTE

a) Write-Word Format

b) Read-Word Format

Legend:
S = Start Condition or Repeated Start Condition P = Stop Condition
ACK = Acknowledge (logic low) NACK = NOT Acknowledge (logic high)
W = Write Bit (logic low) R = Read Bit (logic high)

MASTER TO SLAVE
SLAVE TO MASTER

MAX1667

Chemistry-Independent,
Level 2 Smart Battery Charger

20 ______________________________________________________________________________________

Figure 9. ChargingVoltage() Data to Voltage Mapping

18.416V

16.368V

V

REF

= 4.096V

DCIN > 20V

0V

0b000000000000xxxx

0x000x

0x20Dx 0x47Fx

0b001000001101xxxx

0b010010100000xxxx

0x313x

0b001100010011xxxx

0xFFFx

0b111111111111xxxx

0x106x

0b000100000110xxxx

4.192V

12.592V

ChargingVoltage() D15–D0 DATA

VOLTAGE SET POINT (V0)

8.400V

Figure 10. Average Voltage Between CS and BATT vs. Code

Figure 11. Typical Thermistor Characteristics

1000

100

10

RESISTANCE (kΩ)

1

0.1

-40

-50 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 110

TEMPERATURE (°C)

160 SEL = VL

115

AVERAGE CS-BATT VOLTAGE

IN CURRENT REGULATION (mV)

35

5

0x0080

A:
B:
C:

0x0380 0x0B80 0x0F80 0xFFFF

(128) (896)

0b00001

0b00111 0b10111 0b11111

A: ChargingCurrent( ) CODE (D15–D0)
B: EQUIVALENT DECIMAL CODE
C: CURRENT DAC CODE (DA4–DA0)

(2944) (3968) (65535)

SEL = OPEN

SEL = GND

MAX1667

Chemistry-Independent,

Level 2 Smart Battery Charger

______________________________________________________________________________________ 21

If reverse-polarity protection for the DC input power is
not necessary, diode D4 can be omitted. This eliminates
the power lost due to the voltage drop on diode D4.

Thermistor Characterization

Figure 11 represents the expected electrical behavior
of a 103ETB-type thermistor (nominally 10kΩ at +25°C
±5% or better) to be used with the MAX1667. The
graph is typical of the suggested thermistor’s charac­teristics.

THERMISTOR_OR bit is set only when the thermistor
value is > 100kΩ. This indicates that the thermistor is
open.

THERMISTOR_COLD bit is set only when the thermistor
value is > 30kΩ. The thermistor indicates a cold bat­tery.

THERMISTOR_HOT bit is set only when the thermistor
value is < 3kΩ.

THERMISTOR_UR bit is set only when the thermistor
value is < 500Ω.

Multiple bits may be set depending on the values of the
thermistor (e.g., a 450Ω thermistor will cause both the
THERMISTOR_HOT

and

the THERMISTOR_UR bits to
be set). The thermistor may be replaced by fixed-value
resistors in battery packs that do not require the ther­mistor as a secondary fail-safe indicator. In this case, it
is the responsibility of the battery pack to manipulate
the resistance to obtain correct charger behavior.

Table 4. ChargingCurrent() Bit Functions

2048

DA4

1024

DA3

512

DA2

256

DA1

128

DA0

D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0

WEIGHT IN mA

(R

SENSE

= 40mΩ)

FUNCTION

BIT POSITION

3968*

FS* IOUT**

7**

x

0x0010–0xFFFF

0x0010–0xFFFF

0x0010–0xFFFF

0x0010–0xFFFF

0x0000–0x000F

ChargingVoltage()

0x0000

0x0001–0x0007

0x0001–0x0007

0x0008–0x007F

0x0001–0x0007

000

x

ChargingCurrent()

x

1

0

0

1

x

CCV_LOW

x

0

x

x

1

x

VOLTAGE_

NOTREG

0

0

7

7

7

0

000

000

I

OUT

OUTPUT

CURRENT (mA)

0x0010–0xFFFF

000

000

x

x0x0010–0xFFFF

x

x

0x0010–0xFFFF

0x0008–0x007F

x

0x0080–0xFFFF

x

x

000

0x0008–0x007F

1

x

x

x

x

1

1

x

x

x

x

0

7

0

0

0

0

0

0

0

100

0

000

xx1

x10

000

ALARM_

INHIBITED

(Note 1)

CHARGE_

INHIBITED

Table 5. Relationship Between IOUT Source Current and ChargingCurrent() Value

*

When SEL = VL, values above 0x0F80 set the output current to 3.968A.
When SEL = OPEN, values above 0x0B80 set the output current to 2.944A.
When SEL = GND, values above 0x0380 set the output current to 0.896A.

**

Values below 0x0080 set the output current to 7mA.

Note 1: THERMISTOR_HOT and HOT_STOP and NOT (THERMISTOR_UR).

MAX1667

Chemistry-Independent,
Level 2 Smart Battery Charger

22 ______________________________________________________________________________________

0x000F–0xFFFF 0x0000–0x007F

0x0000–0x000F

ChargingVoltage()

0 No000

x

ChargingCurrent()

0x000F–0xFFFF 0x0100–0x037F

0x000F–0xFFFF

2–6 Yes

N/A

SEL = GND

CURRENT DAC CODE

000

0x0080–0x00FF

No

SEL = GND

SW REG ON?

1 Yes000

0x000F–0xFFFF 0x0400–0x047F

0x000F–0xFFFF

7 Yes000

0x0380–0x03FF

0x000F–0xFFFF 0x0B80–0x0BFF

0x000F–0xFFFF

7 Yes

7

000

0x0480–0x0B7F

Yes

7 Yes000

000

0x000F–0xFFFF 0x0C80

0x000F–0xFFFF

70Yes

0

000

0

0x0C00–0x0C7F

0x000F–0xFFFF 0x1000–0xFFFF

0x000F–0xFFFF

7 Yes

7

000

0x0F80–0x0FFF

Yes

7 Yes000

x x

x

N/A Nox1

ALARM_INHIBITED

0

(Note 1)

CHARGE_INHIBITED

x

x

N/AxNo

N/A Noxx1

100

000

Table 6. Relationship Between Current DAC Code and the ChargingCurrent() Value

x

x

1

x

1

x

x

x

x

1

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

AlarmWarning() DATA BITS

Set ALARM_INHIBITED

Set ALARM_INHIBITED

Set ALARM_INHIBITED

D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0

RESULT

Table 7. Effect of the AlarmWarning() Command

0

0

0

SEL = GND

CURRENT_OR

0

1

1

0

1

1

1

1

1

N/A

N/A

N/A

0

2–6

N/A

SEL = OPEN

CURRENT DAC CODE

1

8

23

7

9–22

23

23

23

23

N/A

N/A

N/A

No

Yes

No

SEL = OPEN

SW REG ON?

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

No

No

No

0

0

0

SEL = OPEN

CURRENT_OR

0

0

0

0

0

1

1

1

1

N/A

N/A

N/A

0

2–6

N/A

SEL = VL

CURRENT DAC CODE

1

8

23

7

9–22

25–30

31

24

31

N/A

N/A

N/A

No

Yes

No

SEL = VL

SW REG ON?

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

No

No

No

0

0

0

SEL = VL

CURRENT_OR

0

0

0

0

0

0

1

0

0

N/A

N/A

N/A

Note 1: THERMISTOR_HOT and HOT_STOP and NOT (THERMISTOR_UR).

MAX1667

Chemistry-Independent,

Level 2 Smart Battery Charger

______________________________________________________________________________________ 23

Table 8. ChargerStatus() Bit Descriptions

DESCRIPTION

0 = Ready to charge a smart battery
1 = Charger is off; IOUT current = 0mA; DLO = PGND; DHI = LX

0 = VL voltage < 4V
1 = VL voltage > 4V

Always returns ‘0’

0 = THM voltage > 5% of REF voltage
1 = THM voltage < 5% of REF voltage

No11

This bit reports the state of an internal SR flip-flop (denoted ALARM_INHIBITED
flip-flop). The ALARM_INHIBITED flip-flop is set whenever the AlarmWarning()
command is written with D15, D14, or D12 set. The ALARM_INHIBITED flip-flop
is cleared whenever BATTERY_PRESENT = 0, or ChargerMode() is written with
POR_RESET = 1, or ChargingVoltage() or ChargingCurrent() is written.

LATCHED?

Yes

No

N/A

BIT

POSITION

0

15

1

AC_PRESENT

0 = No battery is present (THERMISTOR_OR = 1).
1 = A battery is present (THERMISTOR_OR = 0).

Yes

No14

12

BATTERY_PRESENT

0 = BATT voltage < 89% of DCIN voltage
1 = BATT voltage > 89% of DCIN voltage

ALARM_INHIBITED

No13

THERMISTOR_UR

Always returns 0
0 = ChargingCurrent() value is valid for MAX1667.

1 = ChargingCurrent() value exceeds what MAX1667 can actually deliver.
0 = ChargingVoltage() value is valid for MAX1667.

1 = ChargingVoltage() value exceeds what MAX1667 can actually deliver.

N/A

No

No

5

6

7

0 = THM voltage < 91% of REF voltage
1 = THM voltage > 91% of REF voltage

0 = THM voltage < 75% of REF voltage
1 = THM voltage > 75% of REF voltage

This bit reports the state of an internal SR flip-flop (denoted THERMISTOR_HOT
flip-flop). The THERMISTOR_HOT flip-flop is set whenever THM is below 23%
of REF. It is cleared whenever BATTERY_PRESENT = 0 or ChargerMode() is
written with POR_RESET = 1.

No

No

Yes

8

9

10

THERMISTOR_OR

THERMISTOR_COLD

THERMISTOR_HOT

LEVEL_3

CURRENT_OR

VOLTAGE_OR

POWER_FAIL

0 = BATT voltage is limited at the voltage set point (BATT = V0).
1 = BATT voltage is less than the voltage set point (BATT < V0).

Always returns 1

0 = Current through R1 is at its limit (I

BATT

= I0).

1 = Current through R1 is less than its limit (I

BATT

< I0).

No

N/A

No

2

4

3

VOLTAGE_NOTREG

LEVEL_2

NAME

CHARGE_INHIBITED

CURRENT_NOTREG

MASTER_MODE

*

Bit position in the D15–D0 data

N/A = Not applicable

PC Board Layout Considerations

Good PC board layout is required to achieve specified
noise, efficiency, and stable performance. The PC
board layout artist must be given explicit instructions,
preferably a pencil sketch showing the placement of
power-switching components and high-current routing.
Refer to the PC board layout in the MAX1667 evaluation
kit manual for examples. A ground plane is essential for
optimum performance. In most applications, the circuit
will be located on a multilayer board, and full use of the
four or more copper layers is recommended. Use the
top layer for high-current connections, the bottom layer
for quiet connections (REF, CCV, CCI, DACV, GND),
and the inner layers for an uninterrupted ground plane.
Use the following step-by-step guide:

1) Place the high-power components (C1, C6, M1, M2,
D1, L1, and R1) first, with their grounds adjacent:

•

Minimize current-sense resistor trace lengths

and
ensure accurate current sensing with Kelvin con­nections (Figure 12).

•

Minimize ground trace lengths

in the high-current

paths.

•

Minimize other trace lengths

in the high-current

paths:

— Use > 5mm-wide traces.
— Connect CIN to high-side MOSFET drain: 10mm

max length.
— Connect rectifier diode cathode to low side.
— MOSFET: 5mm max length.
— LX node (MOSFETs, rectifier cathode, induc-

tor): 15mm max length.

Ideally, surface-mount power components are butted
up to one another with their ground terminals almost
touching. These high-current grounds are then con­nected to each other with a wide, filled zone of
top-layer copper so they do not go through vias. The
resulting top-layer subground plane is connected to the
normal inner-layer ground plane at the output ground
terminals, which ensures that the IC’s analog ground is
sensing at the supply’s output terminals without interfer­ence from IR drops and ground noise. Other high-cur­rent paths should also be minimized, but focusing
primarily on short ground and current-sense connec­tions eliminates about 90% of all PC board layout prob­lems.

2) Place the IC and signal components. Keep the main
switching nodes (LX nodes) away from sensitive
analog components (current-sense traces and REF
capacitor). Place the IC and analog components on
the opposite side of the board from the power­switching node. Important: The IC must be no fur­ther than 10mm from the current-sense resistors.
Keep the gate-drive traces (DH, DL, and BST) short­er than 20mm and route them away from CSH, CSL,
and REF. Place ceramic bypass capacitors close to
the IC. The bulk capacitors can be placed further
away.

3) Use a single-point star ground where the input
ground trace, power ground (subground plane), and
normal ground plane meet at the supply’s output
ground terminal. Connect both IC ground pins and
all IC bypass capacitors to the normal ground plane.

Upgrading from MAX1647 to MAX1667

The MAX1667 is a pin- and software-compatible
upgrade to the MAX1647, with the following functional
differences:

1) The PWM duty cycle has been extended to 97%.

2) The internal reference has been changed to
+4.096V with 1% accuracy over line, load, and tem­perature.

3) The internal voltage DAC has been changed to allow
a program voltage of 18,416mV. Up to four Li+ cells
can be charged.

4) The linear current source (IOUT) has been reduced
to 7mA and turns off when the switching regulator is
on.

5) An internal diode has been added to the IOUT pin to
prevent reverse current from BATT when the DC
source is removed.

6) The internal current DAC was changed from 6-bit to
5-bit resolution.

MAX1667

Chemistry-Independent,
Level 2 Smart Battery Charger

24 ______________________________________________________________________________________

Figure 12. Kelvin Connections for the Current-Sense Resistors

HIGH-CURRENT PATH

SENSE RESISTOR

MAX1667

MAX1667

Chemistry-Independent,

Level 2 Smart Battery Charger

______________________________________________________________________________________ 25

7) The SEL pin digitally limits the output current to 4A,
3A, or 1A without a change in sense resistor value
between the three modes.

8) The single count current-sense voltage has been
changed to 5mV. R1 required is now 40mΩ.

9) After the AlarmWarning() message, the charger is
not locked off. Subsequent ChargingVoltage() or
ChargingCurrent() commands allow the MAX1667
to resume the charge.

10) The Alert-Response address is 0x13 (0b00010011).

When upgrading a MAX1647 design, follow these rec­ommended or required changes (part numbers refer to
Figure 3 of the MAX1647 data sheet):

1) Change R1 to 40mΩ (required).

2) Remove diodes D5 and D6, transistor Q1, and resis-

tor R6. Connect IOUT directly to BATT (recommend­ed).

3) Remove the external +4.096V reference (recom-

mended).

4) Remove D6 (recommended). When doing this, also

place a small-signal diode in series with R7 and con­nect it directly to the DC source (see D3 and R5 on
Figure 3 of the MAX1647 data sheet).

Pin Configuration

TRANSISTOR COUNT: 6378
SUBSTRATE CONNECTED TO AGND

Chip Information

TOP VIEW

1

IOUT

DCIN

CCV

CCI

SEL

CS

BATT

REF

2

3

VL

4

MAX1667

5

6

7

8

9

10

SSOP

20

19

18

17

16

15

14

13

12

11

BST

LX

DHI

DLO

PGND

DACV

SDA

SCL

THM

INTAGND

MAX1667

Chemistry-Independent,
Level 2 Smart Battery Charger

26 ______________________________________________________________________________________

________________________________________________________Package Information

SSOP.EPS

MAX1667

Chemistry-Independent,

Level 2 Smart Battery Charger

______________________________________________________________________________________ 27

NOTES

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

28

__________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 [phone]

© 1999 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

MAX1667

Chemistry-Independent,
Level 2 Smart Battery Charger

NOTES